Reducing the pollutants and high temperatures of internal combustion engine exhaust gases and the temperatures of hot surfaces in underground mining vehicles is essential to the safety of mine personnel in underground coal mines. Diesel engines exhaust hot sulphurous gases, aldehydes, nitrogen oxide, unburned hydrocarbons and particulate pollutants. Hot exhaust emissions, typically 800.degree.-1000.degree. F., and hot engine surfaces can ignite combustible gases and material present in underground mines, such as methane and coal dust.
Water jacketing the engine's exhaust manifold and piping in conjunction with the engine's cooling system reduces engine surface temperature sufficiently to meet safety requirements. However, the safety hazard and pollution problems caused by hot exhaust emissions require water scrubbers. Scrubbers either aspirate water into the stream of hot exhaust gases or bubble exhaust gases through a water bath to cool them, as shown in U.S. Pat. No. 4,300,924 to Coyle, the disclosure of which is incorporated herein by reference. Because these scrubbers introduce water droplets into the exhaust stream, a water trap is required between the scrubber and a downstream filter element to prevent water from entering the filter. Water traps typically employ a series of interleaved plates to create a labyrinthine path for exhaust gases. Droplets incident on the plates adhere to the plates and are drained away. Without such a water trap, the filter elements become blocked, degraded and damaged as they become wetted by water droplets in the exhaust stream.
Current exhaust treatment systems use separate water scrubbers, water traps, and exhaust filters in series interconnected by exhaust tubing. Such an elongated serially connected system has several disadvantages. If the system is vertically oriented, it is unsuitable for use in most underground mining operations where vertical height is at a premium. The necessary horizontal orientation generally requires substantial lengths of tubing between the components to span between the engine location and a suitable exhaust outlet location, typically at the rear of the vehicle.
Exhaust tubing must be stainless steel to avoid corrosion. Consequently the material cost to construct such an elongated system can be substantial. A serially connected system of discrete components is generally cumbersome to construct and install as well.
In addition, the substantial tubing length creates an efficiency-impairing exhaust back pressure that wastes fuel and decreases vehicle performance.
A further disadvantage of serial systems interconnected by substantially horizontal tubing lengths is that, even with an effective water trap, gaseous water vapor is more likely to condense as it travels further from the source. If there is a sufficient temperature gradient between the scrubber and the filter, condensation may occur in the cooler tubing near the filter. Such condensation may drain into the filter, causing damage, impairing filter function and requiring its premature replacement.
Because of the foregoing problems associated with existing water scrubber and water trap-filter systems, there is a need for an effective system, especially for underground mining vehicles, that overcomes such problems. This, therefore, is the primary objective of the present invention.